Cubic boron nitride (hereafter abbreviated as “CBN”) is a material having high hardness after diamond and low reactivity with metals, and therefore, a sintered body thereof is used for a tool for cutting a heat resistant alloy or quenched steel. Even for the CBN sintered body having such high hardness, a surface covering film is formed thereon to prevent wear of an edge portion.
Patent Document 1 discloses a hard film-covered very high temperature and high pressure sintered body characterized in that peak intensity from a specific crystal surface of a surface covering film (coating) on a CBN sintered body during X-ray diffraction has a specific relation. In this technique, it is proposed to process a cutting edge with beveling or into a honed shape such as an R shape to prevent nicking or chipping. It is also disclosed that when a thickness of the coating decreases toward a cutting edge ridgeline portion, properties regarding peeling of the coating and minute chipping of the cutting edge are improved.
Patent Document 1: Japanese Patent Laying-Open No. 2002-3284